The present invention generally relates to well drilling and completion and, in a preferred embodiment thereof, more particularly relates to packer structures and associated methods utilized in well drilling and completion activities.
In a multilateral well formation method illustrated and described in the aforementioned copending U.S. application Ser. No. 08/296,941 incorporated herein by reference, a hydraulically settable tubular packer structure is operatively installed in a vertical well casing and coaxially supports an orienting nipple. The nipple has a key-receiving vertical locating profile formed on its interior side surface, and additionally has a spiral groove formed on its interior side surface.
After the packer/nipple structure is set in place within the casing, a diverter structure having a drillable core portion is lowered through the casing and passed downwardly through the packer/nipple structure interior. A locating key assembly carried by a lower end portion of the diverter structure snaps into place within the nipple vertical locating profile in a manner stopping further downward travel of the diverter structure and locking it to the nipple and locating the top end of the diverter structure above the top end of the packer/nipple structure at a predetermined vertical position within the well casing. As the diverter structure passes downwardly through the packer/nipple structure, and before the diverter locating key assembly snaps into locked engagement within the nipple vertical locating profile, a spring-loaded orienting lug disposed on the diverter structure enters and spirally traverses the nipple interior surface groove to thereby rotate the diverter structure to a predetermined circumferential orientation within the casing.
Using a sloped upper end face of the installed diverter as a deflecting surface, a suitable boring structure is then used to drill outwardly through the casing, and into the surrounding earth, to establish a lateral extension of the well bore. The newly formed lateral extension of the well is then provided with a concrete-encased lining structure that communicates it with the interior of the casing above the diverter structure. The diverter structure used to facilitate the formation of the lateral well extension blocks off the casing portion above the packer/nipple structure from the casing portion below the packer/nipple structure. In order to re-establish communication between these casing portions it is necessary to drill out the core of the diverter structure.
As will be appreciated, once the packer/nipple structure is set into place within the casing, in a precise vertical location and rotational orientation therein, it is critical to maintain both the vertical position and rotational orientation of the packer/nipple structure during the balance of the following lateral well extension formation procedure including the positioning of the diverter structure in the packer/nipple structure and its subsequent use as a boring tool deflection guide device.
Conventional packers which are mechanically or hydraulically set in place within a well flow conductor such as a casing string are respectively anchored and sealed within the conductor using circumferentially spaced, radially outwardly deflectable toothed metal slip anchors that are driven into biting engagement with the interior side surface of the casing, and an annular resilient seal structure that is axially compressed in a manner radially deforming it outwardly into sealing engagement with the interior side surface of the casing. These conventionally constructed packers are typically subjected primarily to axial loads within the casing, and their anchor structures, when properly set, work well to prevent axial shifting of the packer within the casing.
However, in the packer application just described, the set packer is subjected during various phases of the lateral well portion formation procedure to relatively high rotational forces within the casing, and conventional packer slip anchor structures do not tend to provide sufficient resistance to packer rotation within the casing, after the packer has been set, to prevent packer rotation relative to the casing in this particular packer application. Additionally, a potential problem with conventional packers of the type generally described above is the potential overstressing of their annular resilient seal assemblies during setting of the packer within the casing.
From the foregoing it can readily be seen that a need exists for improved packer apparatus, and associated methods, that eliminates or at least substantially reduces the foregoing anchoring and sealing problems, limitations and disadvantages which are typically associated with conventionally constructed packer assemblies. It is accordingly an object of the present invention to provide such improved packer apparatus and associated methods.